Wafer clamp ring for use in an ionized physical vapor deposition apparatus

• US 6,176,931 B1
• Filed: 10/29/1999
• Issued: 01/23/2001
• Est. Priority Date: 10/29/1999
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Restaino, Darryl D., Cooney, Edward C. III, Simon, Andrew Herbert, Smetana, Pavel, Rossnagel, Stephen Mark
• Primary Examiner(s): Mills, Gregory
• Assistant Examiner(s): Hassanzadeh, Parviz
• Application Number:
  US09/430,829
• Time in Patent Office: 452 Days
• Field of Search: 118/725, 118/500, 118/504, 118/503, 118/52, 118/728, 118/724, 118/715, 118/716, 118/723.E, 156/345, 204/192.1, 204/192.12, 204/298.01, 204/298.06
• US Class Current: 118/715
• CPC Class Codes: C23C 14/50 Substrate holders
• CPC Class Codes: C23C 14/541 Heating or cooling of the substrates

Abstract

Improvements are described for a wafer clamp ring used in an IPVD apparatus to provide cooling for the wafer clamp ring, to protect the wafer clamp ring from ion bombardment, and to prevent damage to the wafer. The wafer clamp ring is placed on a cooling fixture when not required for a deposition process. The fixture is annular in shape and in close thermal contact with a circulating coolant and is thereby cooled below ambient temperature. The cooling line and the cooling fixture are fixed relative to the IPVD device, so that problems associated with flexible cooling lines are avoided. An annular grounded shield may be provided between the plasma and clamp ring to protect the clamp ring against ion bombardment during the deposition process. The wafer clamp ring may have a portion which overhangs the wafer during a deposition process, and which has a ridge portion extending downwards therefrom and tapering to a knife edge. The wafer clamp ring may be fabricated as a split ring with an insulating portion, to prevent heating by induced current in the clamp ring.

Claims

1. A device for cooling a wafer clamp ring used in an ionized physical vapor deposition (IPVD) apparatus, the wafer clamp ring holding the wafer on a wafer pedestal during a deposition process, the device comprising:

a cooling fixture on which the wafer clamp ring is placed when the wafer clamp ring is not required for a deposition process, said fixture being annular in shape and in close thermal contact with a circulating coolant and thereby cooled below ambient temperature,

wherein the bottom surface of the wafer clamp ring is brought into close thermal contact with a top surface of the fixture when the wafer clamp ring is placed thereon, so that the wafer clamp ring is cooled below ambient temperature when not required for a deposition process and is then at a different position with respect to the wafer pedestal than during the deposition process.

2. A device according to claim 1, wherein the coolant is in a cooling line, and the cooling fixture and the cooling line are fixed relative to the IPVD device.

3. A device according to claim 1, wherein the top surface of the fixture has a sloped portion with an inner diameter substantially identical to an outer diameter of the wafer clamp ring, causing the wafer clamp ring to be centered relative to the fixture when the wafer clamp ring is placed thereon.

4. A wafer clamp ring assembly for use in an ionized physical vapor deposition (IPVD) device in which a plasma is formed to facilitate deposition of material on a wafer, the wafer clamp ring assembly comprising:

a wafer clamp ring for holding a wafer during a deposition process, the wafer clamp ring being annular in shape; and

a shield for protecting the wafer clamp ring against ion bombardment during the deposition process, the shield being located between the plasma and the wafer clamp ring and being annular in shape, an inside diameter of the shield and an inside diameter of the wafer clamp ring being substantially identical,

wherein the wafer clamp ring is at a bias potential and the shield is at ground potential during the deposition process.

5. A wafer clamp ring assembly according to claim 4, further comprising a generally cylindrical shield attached to said annular shield and surrounding the wafer clamp ring during the deposition process, said generally cylindrical shield having holes therein to facilitate flow of gases in the IPVD device.

6. A wafer clamp ring assembly according to claim 4, wherein the shield is of a same material as the material deposited on the wafer.

7. A wafer clamp ring assembly according to claim 4, wherein the shield is coated with a material having higher emissivity than the material of the shield.

8. A wafer clamp ring assembly according to claim 4, wherein at least one of the wafer clamp ring and the shield has a surface with a texture facilitating radiative cooling from said surface.

9. A wafer clamp ring assembly for holding a wafer during a deposition process in an ionized physical vapor deposition (IPVD) device in which a plasma is formed to facilitate deposition of material on the wafer, the wafer clamp ring comprising:

a first portion having an annular shape and having an inner diameter less than a diameter of the wafer, the first portion having a bottom surface in contact with the wafer during a deposition process;

a second portion having an annular shape and connected to the first portion so as to overhang the wafer during the deposition process, the second portion having an inner diameter less than the inner diameter of the first portion; and

a ridge portion extending downwards from the second portion and tapering to a knife edge, the knife edge being disposed above the wafer and separated therefrom when the bottom surface of the first portion is in contact with the wafer.

10. A wafer clamp ring assembly according to claim 9, wherein the second portion has an underside facing the wafer during the deposition process and a height defined by a distance between said underside and the wafer, and the ridge portion extends vertically approximately half said height.

11. A wafer clamp ring assembly according to claim 9, wherein the second portion has a width defined by a radial distance between an inner surface of the first portion and an inner surface of the second portion, and the ridge portion extends radially approximately half said width.

12. A wafer clamp ring assembly according to claim 11, wherein the ridge portion is centered in the radial direction with respect to said width.

13. A wafer clamp ring assembly according to claim 9, wherein the wafer clamp ring is of a same material as the material deposited on the wafer.

14. A wafer clamp ring assembly according to claim 9, wherein the wafer clamp ring is coated with a material having higher emissivity than the material of the wafer clamp ring.

15. A wafer clamp ring assembly according to claim 9, wherein the wafer clamp ring has a surface with a texture facilitating radiative cooling from said surface.

16. A wafer clamp ring assembly according to claim 9, further comprising:

a shield for protecting the wafer clamp ring against ion bombardment during the deposition process, the shield being located between the plasma and the wafer clamp ring and being annular in shape, an inside diameter of the shield and an inside diameter of the wafer clamp ring being substantially identical,

wherein the wafer clamp ring is at a bias potential and the shield is at ground potential during the deposition process.

17. A wafer clamp ring assembly according to claim 16, further comprising a generally cylindrical shield attached to said annular shield and surrounding the wafer clamp ring during the deposition process, said generally cylindrical shield having holes therein to facilitate flow of gases in the IPVD device.

18. A wafer clamp ring assembly according to claim 16, wherein the shield is of a same material as the material deposited on the wafer.

19. A wafer clamp ring assembly according to claim 16, wherein the shield is coated with a material having higher emissivity than the material of the shield.

20. A wafer clamp ring assembly according to claim 16, wherein the shield has a surface with a texture facilitating radiative cooling from said surface.

21. A wafer clamp ring for holding a wafer during a deposition process in an ionized physical vapor deposition (IPVD) device in which a plasma is formed to facilitate deposition of material on the wafer, the wafer clamp ring comprising:

a first portion of a conductive material, the first portion having an annular shape with an inner circumference and an outer circumference and with a gap extending from the inner circumference to the outer circumference, so that the first portion is discontinuous in the circumferential direction; and

a second portion of an insulating material disposed in said gap, so that induced current in the wafer clamp ring and heating of the wafer clamp ring due to induced current are avoided.